A wide variety of structures for use in catamenial articles such as sanitary napkins and pantiliners are well-known in the literature. In general, such articles comprise a fluid-permeable topsheet, an absorbent core, and a fluid-impermeable backsheet. Typically, the absorbent core of such articles comprises cellulosic fibers of one type or another. Northern Softwood Kraft, Southern Softwood Kraft, chemi-thermomechanical pulps, and the like, have all been suggested for use as absorbent materials in catamenials. Modern catamenials often contain absorbent gelling materials, such as polyacrylates and starch-acrylate grafts, to provide additional absorbent capacity.
There is a continuing search for more economical, yet effective, absorbent core materials. Moreover, modern catamenial products, especially sanitary napkins and pantiliners, are now becoming available in ultra-thin forms. Such ultra-thin forms provide additional comfort to the wearer, but require especially effective absorbent cores in order to provide the desired absorbency and protection from failure, in-use. In the main, current ultra-thin cores employ a mixture of cellulose fibers and absorbent gelling materials, as noted above.
However, there are drawbacks even to the modern ultra-thin cellulose/absorbent gelling material cores. For example, the use of absorbent gelling materials in manufacturing processes can be problematic, inasmuch as such materials can be dusty and difficult to handle. Moreover, absorbent gelling materials can be expensive. Indeed, absorbent gelling materials were primarily developed to absorb low viscosity fluids such as urine, e.g., in infant diapers, and some types of absorbent gelling materials are not optimally useful with more viscous liquids such as menses. Finally, the formulation of ultra-thin absorbent pads from ordinary cellulosic fibers and absorbent gelling materials often requires the use of latex binders, which can amount to as much as 20% by weight of the total cellulosic fibers in the core. Such binders are necessary to provide strength and cohesiveness to the core during manufacturing operations and also under in-use conditions after the cores become moistened by body fluids.
Until now, the development of absorbent core materials for use in sanitary napkins and pantiliners has relied to a considerable extent on learnings associated with the manufacture of disposable infant diapers. The absorbent gelling materials in both types of products are quite similar. The cellulosic fibers used in both types of products are very similar. Yet, it will be appreciated that the nature of the fluids being absorbed in diapers vs. catamenials is substantially different. Moreover, diapers have much higher volume requirements and a much greater need for moving such higher volumes of liquids through larger distances and heights in the absorbent core than do catamenial products. Thus, having given due consideration to these factors, it has now been determined that cellulosic materials of the type described hereinafter can very admirably serve as the absorbent core in sanitary napkins and pantiliners.
Accordingly, it is an object of the present invention to provide sanitary napkins and pantiliners having improved absorbent cores. While the absorbent cores provided in this invention can optionally contain absorbent gelling materials, it is a further object herein to provide absorbent cores which function sufficiently well, even when ultra-thin, that absorbent gelling materials are not required. It is a further object herein to provide absorbent cores which have high capillarity in conjunction with high permeability, as well as the ability to hold fluids tenaciously. It is a further object herein to provide catamenial articles whose absorbent cores do not require latex binder. These and other objects are secured by the present invention, as will be seen hereinafter.